The inventors of the present invention have developed VSRAD (registered trademark) (Voxel-Based Specific Regional Analysis System for Alzheimer's Disease), which is a diagnosis support system for early stage AD (Alzheimer's Disease). VSRAD is an image processing/statistical analysis software for detecting levels of atrophy in the vicinity of the parahippocampal gyrus (=region of interest), which is characteristically seen in early stage, including prodromal stage, Alzheimer-type dementia, from MRI images.
In VSRAD (registered trademark), the level of atrophy in the region of interest is automatically analyzed, and a Z-score map is superimposed on the MRI brain image. Z-score is a value that indicates the amount of displacement from the average value, in terms of standard deviation, when the image of the test subject and the average image of a healthy subject are statistically compared. In a Z-score map, as in thermography, the distribution of the Z-score is displayed in color according to the Z-score value and is superimposed on the brain image of the test-subject. The diagnostician can visually confirm the degree of atrophy by the Z-score map.
In VSRAD (registered trademark), technologies such as VBM (Voxel Based Morphometry) (see Patent Document 1) and DARTEL (Diffeomorphic Anatomical Registration using Exponentiated Lie algebra) (see Patent Document 2) are used.
VBM is a technology of performing image processing on brain image obtained by imaging the head area of the test subject in units of voxel, which is a three-dimensional picture element. DARTEL shows superior accuracy in spatial standardization processing, compared to conventional VBM, and shows promise in improving diagnostic performance by image statistic analysis for Alzheimer's disease. Here, spatial standardization processing refers to performing broad correction for the size of the entire brain, and local correction for the partial size, in order to internalize the anatomical difference of the brain image between individuals.
In a MRI brain image (especially T1-emphasized MRI brain image), three types of tissue are included, which are the gray colored gray matter corresponding to the nerve cells, the brighter colored white matter corresponding to the nerve fiber, and the almost-black cerebrospinal fluid. By using DARTEL, lesions and degrees of atrophy, which are abnormalities, in the white matter extracted by tissue segmentation of the MRI brain image of the test subject, can be accurately evaluated (see Patent Document 2).